Mangled beams recovered from the area where a hijacked plane hit the north tower more than a decade ago show what some believe to be a face.

A close look toward the top of the structure shows what some have made out to be a face. It has been called the “angel of 9/11.” (AP/Mary Altaffer)

The steel installation, which will be featured at the National September 11 Memorial and Museum opening to the public in the spring of 2014, has been dubbed the “angel of 9/11″ by those who can see the face, according to WNBC-TV.

The exhibit, more formally called “Impact Steel,” is thought to contain metal from between the World Trade Center’s 93rd and 99th floor. Not everyone can see the purported face though. WNBC reported a source at the museum said lighting and viewing angle factor into the face’s visibility.

A photographer take a picture of steel column from the North Tower of the World Trade Center during a media tour of the National September 11 Memorial and Museum, Friday, Sept. 6, 2013 in New York. Construction is racing ahead inside the museum as the 12th anniversary of the Sept. 11, 2001 attacks draws near. Several more large artifacts have been installed in the cavernous space below the World Trade Center memorial plaza. (AP/Mary Altaffer)

After the attack, salts, oxides and moisture on the steel’s surface affected how the girder corroded, said P. Chris Pistorius, a materials scientist at Carnegie Mellon University who is co-director of the Center for Iron and Steelmaking Research. Air circulation around the ruined steel played a role as well.

“Atmospheric corrosion is very sensitive to microclimates,” he told NBC News. “It’s actually difficult to get even corrosion of such a surface. It’s more likely to get a pattern than to get uniform corrosion.”

If layers of steel are lying on top of each other, as appears to have been the case with the 9/11 girder, moisture can “wick in different areas and leave all kinds of different patterns,” said Thomas Eagar, a professor of materials engineering at the Massachusetts Institute of Technology.

While human attributes might be found in the twisted steel, making them into a face could very well be a trick of the mind. A phenomenon known as pareidolia describes when humans see faces in inanimate objects, like the “man in the moon.” The BBC in an article earlier this year explained why we might see such faces in the moon, toast, cloth, etc.:

And the tendency to pick out familiar figures goes back to the first humans, says Christopher French of the British Psychological Society.

“We’ve evolved brains that think in these quick, dirty ways that are usually right, but at times can lead us to systematically be biased,” he explains.

“A classic example is the Stone Age guy standing there, scratching his beard, wondering whether that rustling in the bushes really is a sabre-toothed tiger. You’re much more likely to survive if you assume it’s a sabre-toothed tiger and get the hell out of there – otherwise you may end up as lunch.”

Other experts say pareidolia is a consequence of the brain’s information processing systems. The brain is constantly sifting through random lines, shapes, surfaces and colours, says Joel Voss, a neuroscientist at Northwestern University.

It makes sense of these images by assigning meaning to them – usually by matching them to something stored in long-term knowledge. But sometimes things that are slightly “ambiguous” get matched up with things we can name more easily – resulting in pareidolia, he says.

Michael Shermer with Skeptical Inquirer Magazine and author of “The Believing Brain: From Ghosts and Gods to Politics and Conspiracies” called it “patternicity,” according to CNN. With regard to the angel of 9/11, Shermer said figures that could look like two eyes and a mouth would stimulate the area of the brain that recognizes faces.

“People often find meaning in tragedy, particularly in one as widely felt as the September 11 attacks,” said Anthony Guido, a spokesperson for the 9/11 museum, said in a statement, according to CNN. “This impact steel is historically important to include in the museum as it will help tell the story of 9/11 to visitors from around the world.”